The English sentence is ambiguous. It could mean "My dog is the only thing I keep." It's this meaning that's translated into Hebrew here. For this meaning, the English could use "except" instead of "except for", and "except for" means nothing more than "except". But it could also mean "The only things I keep are things that I use to take care of my dog", in which case I think that בשביל would be part of the translation, and "except for" would be shorthand for "except things that I use for".